Allylic nitro compounds 1 are a synthetically versatile class of structures capable of delivering a wide range of products possessing important structural motifs (Scheme 1). These include α,β-unsaturated ketones 2, allylic amines 3, allylic nitriles 4, unsaturated β-nitro alcohols 5, unsaturated β-amino alcohols 6, unsaturated α-nitro ketones 7, 2-nitro-1,3-dienes 8 as well as further functionalized products 9.

The nitro-aldol or Henry reaction is a widely used tool for the construction of conjugated nitroalkanes 10 (Henry, Compt. Rend. 1895, 120, 1265; Wang, Henry Reaction. In Comprehensive Organic Name Reactions and Reagents, John Wiley & Sons, Inc.: 2010). In 1982, Barton et al. detailed the use of imine catalysis for irregular nitro-aldol reactions which gave allylic nitro compounds 11 useful in the synthesis of corticosteroids (Barton et al., J. Chem. Soc., Chem. Commun. 1982, 551-552). This was later explored in more detail by Tamura et al. (J. Org. Chem. 1986, 51, 4368-4375). Where it was shown that N,N-dimethylethylenediamine 12 could be used as a catalyst for the formation of allylic nitro compounds from ketones and primary nitroalkanes (Scheme 2).

The methodology developed by Barton and Tamura was used recently for the synthesis of symmetrical cycloalkene allylic nitro compounds (Umemiya et al., Chem. Eur. J. 2014, 20, 15753-59). For all of these developed nitro-aldol reactions, benzene was used as a solvent for azeotropic removal of water formed during the reaction. However, the use of benzene is now heavily regulated. In addition, it has received no attention with regards to the selective preparation of asymmetric cyclic allylic nitro compounds since these initial discoveries in 1982/1986. There is a need to develop a green and efficient process to prepare cyclic allylic nitro compounds.